These sites are known in Irish as cilліní (singular cillín), small unconsecrated or semi-consecrated plots where unbaptised infants, and sometimes others excluded from formal Church burial, were laid to rest. They occupy an ambiguous space in Irish religious and social life, neither fully inside nor fully outside the community's ritual landscape, often found at the edges of bogs, old ringforts, or ancient ecclesiastical enclosures.

The practice of burying unbaptised children separately from the main churchyard reflected Catholic theological doctrine on limbo, the state believed to await souls who died before baptism. Though limbo was never formal dogma, it shaped folk practice profoundly, and grieving families had little choice but to bury infants in these marginal plots, typically without ceremony and often at night or in the early morning. Cilліní are found across Ireland in their thousands, and Clare, with its dense concentration of early medieval and later landscape features, has a particularly notable number. The Ballyillaun site is one such place, recorded as a monument but with relatively little detail currently available in the public domain about its physical character, condition, or precise history.

These burial grounds tend to be modest in appearance, easily overlooked. Some are marked by small rough stones, others by nothing visible at all. Their significance lies not in any formal architecture but in what they represent: a long history of private grief managed largely outside official channels, by families and communities making the best of constrained circumstances.